1. Field of the Invention
The present invention relates to an expandable tissue anchor, and more specifically, to an expandable, biodegradable tissue anchor for use in arthroscopic surgical shoulder repair.
2. Description of the Related Art
Expandable anchors are known for use in surgical applications. Examples include U.S. Pat. Nos. 5,268,001 and 5,968,044 to Nicholson et al., which disclose a bone fastener having an expandable sleeve with an axial bore, and a pin with an outer diameter greater than an inner diameter of at least a portion of the axial bore for expanding the sleeve. A holder is severably attached to the sleeve for use during installation. U.S. Pat. No. 5,336,240 to Metzler et al. discloses an expandable anchor in which a pin is pulled proximally to deploy the device.
Other expandable anchors are known for anchoring to building materials such as brick and concrete. For example, U.S. Pat. No. 4,871,289 to Choiniere discloses an expandable anchor with an expanding pin. The pin has a radial shoulder such that the pin locks inside the expandable anchor sleeve after insertion and expansion.
All of these prior art devices require a pre-drilled hole for installation of the anchor. The anchor is placed into the pre-drilled hole and then expanded to provide fixation.
Accordingly, a need exists in the prior art for an expandable anchor that does not require pre-drilling of a bore that accommodates the anchor.
The present invention provides an expandable anchor that is driven into bone without the need for pre-drilling a bore to accommodate the anchor. The anchor utilizes an inner dowel pin, preferably made of a bioabsorbable material such as PLLA, to expand the anchor after it is pushed into place in the bone, and to hold the pin within the anchor. During insertion, the spreadable tip of the anchor is held together by a frangible connection formed of a non-slotted section at the tip of the anchor. As the dowel pin is advanced and the anchor legs spread, the connections are severed to allow complete expansion. In certain types of bone, it may be necessary to punch or drill a small hole to receive the tip of the anchor. Typically, however, no pre-drilling of bone is required.
Advantageously, the non-slotted section allows for driving the device into hard bone without prematurely expanding. Preferably, the push in dowel is made up of low molecular weight polymer to expand in a short period to fixate the dowel as well as increase the overall expansion of the device. In addition, the head is radiused to contour with the anatomical shape of the soft tissue and underlying bone.
Other features and advantages of the present invention will become apparent from the following description of the invention which refers to the accompanying drawings.